Relationship of plasma corticosterone and adrenal cholesterol and corticosterone to the production of soft-shelled and shell-less eggs

Research progress on bird eggshell quality defects: a review

The eggshell quality declined with extending of chicken laying cycles. Eggshell quality is a crucial feature that not only affects consumer preference, but also influences producers' economic profitability. The eggshell ultrastructure consists of mammillary, palisade, and vertical crystal layers. Any defect in shell structure results in a reduction in eggshell quality. Speckled, translucent, pimpled, and soft eggshells are common defects that cause significant financial losses for farmers and food security concerns for consumers. Therefore, reducing the faulty eggshells is critical for poultry production. Defective eggshell quality has been attributed to hereditary factors and external environmental stimuli. As such, improvements can be carried out through selective breeding and environmental control of components such as temperature, moisture, and diet formula balance. In this review, the molecular mechanisms of the main eggshell quality defects (speckled, translucent, pimpled, broken, and soft-shell eggs) and the relevant improvement methods are detailed. We hope this review will serve as a useful resource for poultry production management and effectively increasing eggshell quality.

Effects of dietary corticosterone on yolk colors and eggshell quality in laying hens

The objective of this study was to investigate the effects of dietary corticosterone on egg quality. For 2 weeks hens received either control or experimental diet containing corticosterone at 30 mg/kg diet. Feed intake and egg production were monitored daily, and body weight measured weekly. Egg weights and egg quality were measured daily. Corticosterone treatment resulted in a remarkable increase in feed intake and sharp decrease in egg production compared with control (p<0.05) whereas body weight remained unchanged. Decreased albumen height, but no changes in egg weight, led to decreased Haugh unit (p<0.05). Corticosterone caused elevated eggshell thickness (p<0.05) without altering weight and strength, suggesting possible changes in shell structure. Yolk color and redness were increased by corticosterone (p<0.05) but lightness and yellowness were either not changed or inconsistent over the time period of measurements. Increased concentrations in plasma were also found for corticosterone, glucose, cholesterol, creatinine, uric acid, albumin, aspartate aminotransferase, creatine kinase, lactate dehydrogenase, total protein, and amylase (p<0.05), suggesting that corticosterone increased protein breakdown, renal dysfunctions and pancreatitis. Together, the current results imply that dietary corticosterone affects egg quality such as yolk colors and shell thickness, in addition to its effects on feed intake and egg production.

Group selection for adaptation to multiple-hen cages: hematology and adrenal function

A selected line of White Leghorns that has shown improved survivability and productivity and reduced feather loss in multiple-hen cages was evaluated for hematological and adrenal responses under both stressed and unstressed conditions. It was hypothesized that hens selected for adaptation to multiple-bird cages would react less intensely to stressors. Three lines of chickens (selected, control, and commercial) were housed in either single-hen (1 hen) or multiple-hen cages (12 hens, social competition) at 16.7 or 17.1 wk of age. They were subsequently subjected to cold exposure at 33 wk of age and heat exposure at 44 wk of age. Genetic stock as a main effect, and the interaction of genetic stock with either a cold or heated environment or with cage size, had no effect on plasma levels of cholesterol and corticosterone. At the time of transfer to laying cages, the selected line of pullets, as indicated by a decrease in packed cell volume, appeared to adapt more quickly to the new waterer system of multiple-hen cages than did the control and commercial lines. At 33 wk of age, the control and commercial lines in multiple-hen cages experienced heterophilia and increased heterophil to lymphocyte ratios, whereas the selected line did not, when compared with these same lines in single-hen cages. This leucocytic response could be interpreted to mean that the selected line of chickens adapted better to social competition than either the control or commercial lines; however, a similar leucocytic response was not observed at 18 or 44 wk of age. In conclusion, the physiological characterization of the selected line of Leghorns showed evidence of improved adaptation to multiple-hen cages when compared to the other stocks. In some cases, the selected line responded less intensely to stress; however, trends were not always consistent.

Influence of chlorinated hydrocarbons, Hg2+ and methyl-Hg+ on steroid hormone receptors from eggshell gland mucosa of domestic fowls and ducks

A series of chlorinated hydrocarbons were investigated for their ability to inhibit the binding of tritiated progesterone, dexamethasone and testosterone to their respective cytoplasmic receptors, prepared from the eggshell gland mucosa of the domestic fowl. o,p'-DDE and toxaphene were most potent in inhibiting the binding of progesterone and testosterone to their receptors, while p,p'-DDE was most potent in inhibiting the binding of dexamethasone. The effect of the latter compound on dexamethasone binding was biphasic. There were significant differences between ducks and domestic fowls in the dissociation constant (KD) and maximal number of binding sites (Bmax) for several of the steroid hormones. No effect of steroid binding was observed in the p,p'-DDE-treated ducks that were laying thin-shelled eggs. Some metals were also tested for their ability to inhibit progesterone binding. Hg2+ was most potent (IC50 = 5.8 x 10(-5) M) in this respect, while Cd2+, Pb2+ and Al3+ inhibited the binding only when administered in very high concentrations (10(-3) M). Me-Hg+ was less potent than Hg2+. It is concluded that chlorinated hydrocarbon pesticides may interact with several different steroid hormone receptors. These findings are discussed in relation to some reproductive and other hormonal disturbances observed in birds and mammals.